- The investigators' primary hypothesis is that non-blinded, random, parallel allocation of 12.5mg daily Chlorthalidone (titrated to 25mg at 4 weeks) will demonstrate a clinically meaningful ≥5mmHg improvement in BP control (as measured by change in BP from baseline using 24hr ABPM) compared to 25mg daily HCTZ (titrated to 50mg at 4 weeks) in newly hypertensive patients followed in a usual-care clinic setting over 8 weeks. They will also analyze differences in side-effects or safety (serum electrolytes) between these two medications.